Add ntp module to facilitate NTP-related code

Since we now set up NTP in Anaconda, we need a module providing some
supporting NTP-related functions.

1 files changed, 151 insertions, 0 deletions

diff --git a/pyanaconda/ntp.py b/pyanaconda/ntp.py
new file mode 100644
index 000000000..8e38ce331
--- /dev/null
+++ b/pyanaconda/ntp.py
@@ -0,0 +1,151 @@
+#
+# Copyright (C) 2012  Red Hat, Inc.
+#
+# This copyrighted material is made available to anyone wishing to use,
+# modify, copy, or redistribute it subject to the terms and conditions of
+# the GNU General Public License v.2, or (at your option) any later version.
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY expressed or implied, including the implied warranties of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
+# Public License for more details.  You should have received a copy of the
+# GNU General Public License along with this program; if not, write to the
+# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.  Any Red Hat trademarks that are incorporated in the
+# source code or documentation are not subject to the GNU General Public
+# License and may only be used or replicated with the express permission of
+# Red Hat, Inc.
+#
+# Red Hat Author(s): Vratislav Podzimek <vpodzime@redhat.com>
+#
+
+"""
+Module facilitating the work with NTP servers and NTP daemon's configuration
+
+"""
+
+import re, os, tempfile
+
+NTP_CONFIG_FILE = "/etc/chrony.conf"
+
+#example line:
+#server 0.fedora.pool.ntp.org iburst
+SRV_LINE_REGEXP = re.compile(r"^\s*server\s*([-a-zA-Z.0-9]+)\s*[a-zA-Z]+\s*$")
+
+class NTPconfigError(Exception):
+    """Exception class for NTP related problems"""
+    pass
+
+def ntp_server_working(server):
+    """
+    Runs rdate to try to connect to the $server (timeout may take some time).
+
+    @return: True if the given server is reachable and working, False otherwise
+
+    """
+
+    #FIXME: It would be nice to use execWithRedirect here, but it is not
+    #       thread-safe and hangs if this function is called from threads.
+    #       By using tee (and block-buffered pipes) it is also much slower.
+    #we just need to know the exit status
+    retc = os.system("rdate -p %s &>/dev/null" % server)
+
+    return retc == 0
+
+def get_servers_from_config(conf_file_path=NTP_CONFIG_FILE,
+                            srv_regexp=SRV_LINE_REGEXP):
+    """
+    Goes through the chronyd's configuration file looking for lines starting
+    with 'server'.
+
+    @return: servers found in the chronyd's configuration
+    @rtype: list
+
+    """
+
+    ret = list()
+
+    try:
+        with open(conf_file_path, "r") as conf_file:
+            line = conf_file.readline()
+            while line:
+                match = srv_regexp.match(line)
+                if match:
+                    ret.append(match.group(1))
+
+                line = conf_file.readline()
+
+    except IOError as ioerr:
+        msg = "Cannot open config file %s for reading (%s)" % (conf_file_path,
+                                                               ioerr.strerror)
+        raise NTPconfigError(msg)
+
+    return ret
+
+def save_servers_to_config(servers, conf_file_path=NTP_CONFIG_FILE,
+                           srv_regexp=SRV_LINE_REGEXP, out_file_path=None):
+    """
+    Replaces the servers defined in the chronyd's configuration file with
+    the given ones. If the out_file is not None, then it is used for the
+    resulting config.
+
+    @type servers: iterable
+    @param out_file_path: path to the file used for the resulting config
+
+    """
+
+    try:
+        old_conf_file = open(conf_file_path, "r")
+
+    except IOError as ioerr:
+        msg = "Cannot open config file %s for reading (%s)" % (conf_file_path,
+                                                               ioerr.strerror)
+        raise NTPconfigError(msg)
+
+    try:
+        if out_file_path:
+            new_conf_file = open(out_file_path, "w")
+        else:
+            (fildes, temp_path) = tempfile.mkstemp()
+            new_conf_file = os.fdopen(fildes, "w")
+
+    except IOError as ioerr:
+        if out_file_path:
+            msg = "Cannot open new config file %s "\
+                  "for writing (%s)" % (out_file_path, ioerr.strerror)
+        else:
+            msg = "Cannot open temporary file %s "\
+                  "for writing (%s)" % (temp_path, ioerr.strerror)
+
+        raise NTPconfigError(msg)
+
+    heading = "# These servers were defined in the installation:\n"
+
+    #write info about the origin of the following lines
+    new_conf_file.write(heading)
+
+    #write new servers
+    for server in servers:
+        new_conf_file.write("server " + server + " iburst\n")
+
+    #copy non-server lines from the old config and skip our heading
+    line = old_conf_file.readline()
+    while line:
+        if not srv_regexp.match(line) and line != heading:
+            new_conf_file.write(line)
+
+        line = old_conf_file.readline()
+
+    if not out_file_path:
+        try:
+            stat = os.stat(conf_file_path)
+            os.rename(temp_path, conf_file_path)
+            os.chmod(conf_file_path, stat.st_mode)
+
+        except OSError as oserr:
+            msg = "Cannot replace the old config with "\
+                  "the new one (%s)" % (oserr.strerror)
+
+            raise NTPconfigError(msg)
+
+    old_conf_file.close()
+    new_conf_file.close()